RFC 1993 (rfc1993) - Page 2 of 6

PPP Gandalf FZA Compression Protocol

RFC 1993                      Gandalf FZA                    August 1996


2.  FZA Packets

   Before any FZA packets may be communicated, PPP must reach the
   Network-Layer Protocol phase.

   When the Compression Control Protocol (CCP) has reached the Opened
   state, and FZA is negotiated as the primary compression algorithm,
   the PPP Protocol field indicates type hex 00FB (link compressed
   datagram), or type hex 00FD (compressed datagram).

   The maximum length of the FZA datagram transmitted over a PPP link is
   the same as the maximum length of the Information field of a PPP
   encapsulated packet.

   Padding

      The FZA packets require the negotiation of the Self-Describing-
      Padding Configuration Option [5] at LCP Link Establishment.

   Reliability and Sequencing

      The FZA algorithm expects a reliable link, as described in "PPP
      Reliable Transmission" [6].

      FZA expects the packets to be delivered in sequence.

   Data Expansion

      The maximum expansion of Gandalf FZA is 2:1.  However, typical
      expansion on pre-compressed data is 1.01:1.  Expanded data is sent
      to maintain the integrity of the compression history.

      When the expansion exceeds the size of the peer's Maximum Receive
      Unit for the link, the expanded packet is sent in multiple PPP
      frames.  The compressed data contains an indication of the end of
      the original packet.















Barbir, Carr & Simpson